1. Field of the Invention
This invention relates to a structural fabrication arrangement for forming metal web towers and the like, where the structure is fabricated in a collapsed state in a shop setting and moved to a site for erection.
2. Prior Art
Numerous prefabricated tower configurations are currently available and restructuring and redesign is occurring in this and related areas for fabricating, in a factory setting, lattice towers and like structures for movement to a job site in a demounted state. Such structures, like the present invention, may include interconnected steel plates and braces for supporting and transferring loads. Support structures, such as electrical transmission towers, because of their size and bulk, have necessitated that they be assembled either from individual components or from prefabricated sections at a site for lifting into place as with a crane, or in recent times, a helicopter. Where parts or sections of such towers have been prefabricated for connection together at a site, the assembly of such a tower has still consumed a great amount of time and labor. Also, of course, handling of prefabricated tower sections has been difficult and expensive, particularly considering the areas where such towers are commonly installed. Additionally, as such towers must be individually erected by a crew bolting together the various components or component assemblies, such bolting process has required both a large amount of time to complete, and has generally required that each individual junction thereafter be weather sealed to avoid tower deterioration.
Distinct from such earlier tower structures and their assembly processes for constructing electrical transmission towers, and the like, the present invention provides for fabrication of a tower in a flat plate state, which flat plate can be easily moved to an erection site. Thereat, it is erected by maintaining the base corners and lifting vertically at a center portion thereof to telescope the tower lattice frame in sections or tiers therefrom, forming a three dimensionally, longitudinally tapered structure. The structure is thereafter fixed at its base corners and continuous corner members are connected to each corner plate of each tier as by bolting or welding that corner thereto. Additionally, unique to the present invention, the components that make up the tower structure are easily assembled in a factory setting in a flat plate configuration, that configuration facilitating painting, dipping, or applying a like covering to the plate components for corrosion protection.
The prior art contains a number of examples of structures that are fabricated to be collapsible for erection at a site. Some examples of such arrangements are shown in patents by Lyons, U.S. Pat. No. 3,751,863; Webb, U.S. Pat. No. 3,486,279; Lotto, et al., U.S. Pat. No. 4,017,932 and Bain, U.S. Pat. No. 4,089,147, all of which show tower type structures formed to be erected at a site. These structures, however, do not involve the flat plate nesting assembly of individual components of the tower lattice structure of the present invention nor are the components functionally similar. Other modular construction arrangements that involve foldable, collapsible, self-supporting structures, other than towers, are shown in patents by Schmidt et al., U.S. Pat. No. 3,557,500; Kelly et al., U.S. Pat. No. 3,888,056; Zeigler, U.S. Pat. No. 3,968,808; and Bliss, U.S. Pat. No. 4,243,284. These structures, while they may be collapsible in that they fold accordian style, are not assembled into or from a flat plate structure as is the present invention, nor are the components thereof arranged like nor do they function like those of the present invention.
Additional to the modular towers and support structures cited above, the prior art includes a number of examples of collapsing tower arrangements that include pivoting arms arranged in scissoring configuration. Such structures, however, generally suffer from the same problem of other collapsible assemblies in that the members collapse one upon another, accordian style, forming a stack of pivotally linked sides. Examples of this type of scissoring structure are shown in patents by Audet, U.S. Pat. No. 1,114,718; Berry, U.S. Pat. No. 3,435,570; and Hardin, U.S. Pat. No. 4,126,974. Somewhat different from these scissoring tower patents, however, is a structure shown in a patent by Luckey, U.S. Pat. No. 3,672,104. The Luckey patent while it shows scissoring links, provides for pivotally coupling the links of each tier side such that they are joined in crossover configuration with the sets of links forming each tier to nest alongside one another, successively inwardly, towards the structure center. This nesting configuration is not, however, flat as is taught by the present invention, as its height will be the width of two links, and, of course, the components thereof are different from those of the present invention, as is the way the structure is fabricated from what is taught by the present invention.
Additionally, a novelty patent by Foster, U.S. Pat. No. 1,162,230 while it shows a paper cut out that is somewhat similar in principal to the present invention, is distinct therefrom in that it involves a paper spring structure that is formed by cutting arcs at spaced distances from the center of a sheet of paper. This Foster patent does not teach forming a tower or support structure, and therefore is, of course, in an entirely different and unrelated area of art than is the present invention.